1. Field of the Invention
The invention relates to an indicator device, and more particularly to a diaphragm-type pressure gauge having a movement amplifying mechanism.
2. Description of the Related Technology
Indicator gauges are instruments or meters which are utilized to monitor various parameters such as temperature, pressure, liquid levels or various electric properties. These instruments are specifically configured to give an indication of the monitored condition.
In prior gauges, the sensed condition is typically detected by a bourdon tube or a diaphragm. Both the bourdon tube and diaphragm-type instruments do have inherent drawbacks.
The bourdon tube instrument commonly utilizes a gear and pinion type movement. In the event of severe overpressure conditions--which happen quite frequently--the bourdon tube itself, at about one and a half times maximum operating range, will distort and either run the gear movement off track--thereby rendering itself useless--or reach a critical point within its elastic range and refuse to return to zero. In either case, the instrument is all but destroyed.
On the other hand, the diaphragm-type indicator gauge, especially those constructed according to U.S. Pat. No. 3,375,718, the disclosure of which is expressly incorporated herein, is protected up to two or three times overpressure due to the bottoming out of the diaphragm, but does not lend itself to maximum readout visibility because of the approximate 60.degree. scale pointer arc. In contrast, a bourdon tube gauge typically has a maximum readout visibility of approximately 270.degree. scale pointer arc.